Unusually, it might be neither. Last week Wikileaks posted a link to a copy of a database, in comma-separated variable form, which Royal Mail has confirmed is a copy of its PostZon product , which contains a longitude/latitude pair, NHS ward and county location for every one of the UK's 1.8m postcodes.

Given that Royal Mail charges from £50 (for a single user annual licence) to £25,000 (for a corporate annual licence) for PostZon, you might expect this leak to have a noticeable effect on its revenues for the product – and also lead to an army of web developers using the data for free to cross-reference postcodes against maps.

Such postcode lookups are used all the time, for instance in web applications that try to show amenities near to your location or that do route planning.

But the initial signs are that that won't happen. While many developers are eager to access a lookup table for postcodes, there is considerable distrust among the community that the PostZon database is "clean" – that is, contains no intentionally wrong entries that Royal Mail could use to identify unlicensed use.

Such an intentional mistake – known as a Mountweazel or Nihilartikel – effectively poisons the database to unlicensed users, because its presence proves that the data was copied rather than created from scratch. (Under EU database laws, Royal Mail owns the copyright in the list even without such entries, but would have to demonstrate that all the entries could only have come from its database – a tougher task than finding the planted error.)

The Royal Mail would not say if the database contains such errors: "We don't discuss our security procedures for protecting our intellectual property," said a spokesman – though clearly those procedures have broken down on at least one level. And what economic harm might Royal Mail suffer through this leak? "We're not discussing that," said the spokesman.

Guardian Technology's Free Our Data campaign argues that the PostZon database – and the other Royal Mail location databases, principally its Postcode Address File (PAF), with postcode details for 18m locations – should be available for free, without copyright, so that everyone can use them without having to rely on third-party lookup systems (from organisations such as Google and Yahoo, which provide an API to their own versions of PostZon).

In the meantime, there are still crowdsourcing efforts going on to create copyright-free postcode lists: the New Popular Edition Maps site has a collection of open-sourced postcode locations – although there are presently only 58,000 postcodes in the collected list (which also includes those from Free The Postcode). But one thing's certain: none of them come from the Royal Mail.